The instant invention relates to a spinning process and to a device for the production of yarn.
It is known from DE 34 41 495 that the fiber material for yarn is deposited in form of individual fibers on a collection surface moving in direction of yarn draw-off for the production of a yarn of good quality at high production speed. This fiber material is then withdrawn continuously in form of a yarn while being imparted a twist. The already finished yarn is not overfed with fibers but the latter are conveyed to the yarn end. An oriented deposit of the fibers on the collection surface is achieved by feeding the individual fibers in direction of the movement of the collection surface. The fiber material is bundled and/or doubled into a fiber sliver with the fiber mass sufficient for the desired yarn on the collection surface. The surface speed of the collection surface is approximately equal to the yarn draw-off speed so that the full mass of fibers required for the completed yarn is already collected on the collection surface, is conveyed in closed fiber formation in direction of the twisting element and is twisted into a yarn. This does not however always lead to the desired yarn of good quality. A draft with the ensuing further parallel positioning of the fibers is effected in a preferred embodiment by providing for a surface speed of the collection surface that is lower than the yarn draw-off speed. The fibers are thereby stretched as they are drawn off from the collection surface.
It is a disadvantage in this system that the fibers flying out of the opening roller are compressed as they impact the collection surface.
Another known art is DD 264.944 A1 which discloses fiber applicators for internal friction spinning devices for the precise feeding and stretching of the supplied and opened fibers. The fibers are stretched axially in a fiber applicator and slide from the fiber applicator on the concave internal surface of a friction bell. The rotation of the friction bell causes the fibers to be fed to an easily twisted fiber tuft which is imparted its twist by rolling against concave inner surface of the friction bell together with the sucking action of air exhaust bores. The yarn which is now collected into a completed yarn cross-section is imparted further twist between the surfaces of the downstream friction roller and the concave friction bell rotating in opposite directions. An even higher degree of twist acting counter to the back-twist torque can be achieved by means of a downstream twist-imparter.
It is a disadvantage in this device that the fiber tuft is easily twisted and thereby prevents great yarn uniformity because considerable fluctuations of the spinning tension have an unfavorable influence on the yarn quality. It is a further disadvantage that the yarn is held between the surfaces of the friction roller and of the concave friction bell rotating in opposite directions merely by the easily twisted fiber tuft. Thus a yarn twist between friction roller and friction bell that is independent of the speed of the collection surface is not possible. An additional twist-imparter is therefore installed after the friction roller and the friction bell.